Optical Fiber Diffraction Grating Sensor Based On MZI

after decades of development,optical fiber sensing technology has been applied to all aspects of human development,providing a more convenient sensing method for various work and improving people’s living standards.Mach Zehnder interferometer is an important branch of optical fiber interferometric sensors.Different from the fiber Bragg grating,the fiber diffraction grating proposed in this paper more restores the light splitting ability of the diffraction grating in space.A novel optical fiber sensor is proposed by using the interference of diffracted light and zero order light.This paper mainly studies and experiments the fabrication of diffraction grating in optical fiber and its application in sensing,and puts forward and solves many problems in the application of diffraction grating in the field of optical fiber sensing from both theoretical and experimental aspects.The specific contents are as follows:1.the variation law of diffraction spectrum is summarized according to the diffraction grating theory.Then,the influence of grating parameters on the diffraction efficiency of diffraction grating is verified by simulation.2.Using femtosecond laser micromachining technology,different diffraction grating structures in optical fiber are fabricated,and finally the diffraction grating with excellent diffraction effect is successfully obtained in optical fiber.The differences and similarities of diffraction gratings in single-mode fiber and multimode fiber are analyzed and summarized.3.According to the principle of Mach Zehnder interferometer,a pair of diffraction gratings are made in the optical fiber,and the approximate paths of the two optical paths constituting the Mach Zehnder interferometer are analyzed.Through the diffraction angle of the diffraction grating,the required optical path difference can be set to make the optical fiber sensor.The transmission loss of a pair of diffraction gratings at different intervals is measured.The free spectral range of the transmission spectrum of diffraction grating pairs with different intervals is different,and their interference modes are also different.This paper analyzes the reasons for the changes.The temperature sensitivity of the sensor is 8.03 pm / ℃ in the range of 20-80 ℃,and the strain sensitivity is-1.43pm/με in the range of 0-2000με,The refractive index sensitivity is 363.41nm/RIU in the range of 1.3367-1.3700.